The research examines the ways in which hypotheses are tested against and modified by information which confirms or disconfirms them. The hypotheses with which we are concerned are the types that people form in their everyday social environments. A model of the hypothesis-testing process has been proposed, and research will test the assumptions and implications of the model. One major concern of the research is to determine when and why hypotheses are resistant to change despite disconfirming evidence. A second purpose is to compare the effects of confirmations with the effects of disconfirmations on modifying beliefs. The hypothesis that confirmations have a greater impact on increasing beliefs than disconfirmations have on decreasing beliefs will be tested, and several variables likely to affect this difference will be examined. The third issue to be addressed is when and why people make their behavior either consistent or inconsistent with their own and others' expectations.